Bus duct plug



29, 1967 G- N. JORGENSEN ETAL 3,339,033

BUS DUCT PLUG Filed April 14, 1966 5 Sheets-Sheet l M In" LAWRENCE VINCENT ALLAN ESL/GER G. N. JORGENSEN ETAL 3,339,038

Aug. 29, 1967 BUS DUCT PLUG Filed April 14, 1966 S Sheets-Sheet 2 lNVENTORS JORGENSEN LAWRENCE VINCENT ALLAN E. .SL/CEf? GEORGE /v.

29, 1967 G- N. JORGENSENQ ETAL 3,339,038

BUS DUCT PLUG 5 Sheets-Sheet Filed April 14, v 1966 \mQ QQNT GEORGE /V. J0

T N 1 6 m H m W .H E. ME i M WM AL LAY Aug. 29, 1967 N. JORGENSEN ETAL 3,339,038

BUS DUCT PLUG Filed April 14, 1966 5 Sheets-Sheet 4 L) //Vl/E /V TORS 9 $2 GEORGE N JORGENSEN LAWRENCE VINCENT ALLAN E. SL/CER GLJ M United States Patent 3,339,038 BUS DUCT PLUG George N. Jorgensen, Lawrence Vincent, and Allan E. Slicer, Lexington, Ky., assignors to Square D Company, Park Ridge, 111., a corporation of Michigan Filed Apr. 14, 1966, Ser- No. 542,532 8 Claims. (Cl. 200-50) This invention relates generally to duct plugs for plugin bus duct, and more particularly to interlocking and clamping mechanism therefor.

An object of the invention is to provide a duct plug including a housing and an interlocking mechanism disposed on the outside of the housing so that the interlocking mechanism can be readily understood and inspected, the interlocking mechanism preventing the duct plug from being plugged in or removed from a bus duct while the switch blades of the duct plug are in ON position.

Another object is to provide a duct plug including a housing and a screw disposed on the outside of the housing, the screw being operable to perform both clamping and interlocking functions.

A further object is to provide a duct plug including a housing, a switch mechanism in the housing, and an operating handle outside the housing, the switch mechanism including a plurality of flat blades disposed in flatwise parallel relationship and mounted for edgewise pivotal movement substantially in horizontal planes in the normal position of use of the duct plug, and the operating handle being operatively connected to the switch blades and mounted on a vertical side wall of the housing in the normal position of use of the duct plug.

Other objects will become apparent when the following specification is considered along with the accompanying drawings, in which:

FIG. 1 is a reduced front elevational view of a duct plug constructed in accordance with the invention, the duct plug being mounted on, clamped to, and plugged into a bus duct cooperable therewith and fragmentarily shown;

FIG. 2 is a left side elevational view of the duct plug of FIG. 1 and a fragmentary sectional view of the bus duct of FIG. 1;

FIG. 3 is a front elevational view of the duct plug of FIG. 1, a portion of the front cover being broken away and an arc suppressor assembly being omitted;

FIG. 4 is a bottom plan view of the duct plug of FIG. 1, portions of the housing being broken away;

FIG. 5 is a fragmentary top plan view of the duct plug of FIG. 1;

FIG. 6 is a fragmentary sectional view taken along the line 6-6 of FIG. 3;

FIG. 7 is a fragmentary sectional view taken along the line 7-7 of FIG. 3;

FIG. 8 is a fragmentary sectional view taken along the line 8-8 of FIG. 2;

FIG. 9 is a fragmentary sectional view taken along the line 9-9 of FIG. 2; and

FIG. 10 is a fragmentary rear elevational view of the ductplug of FIG. 1.

With reference to the drawings, a duct plug 20 constructed in accordance with the invention includes a housing having a box 22 and a front cover 24, the cover being pivotally mounted on a front edge portion of a right-hand side wall 22a of the box. The duct plug 20 is adapted to be plugged into a bus duct 26, as shown in FIGS. 1 and 2.

An insulating base 28 and a curved insulating shield 29 (FIGS. 3 and4) are secured to a rear wall portion 22b of the box 22 by a pair of screws 3-0. Secured to the base 28 are three fuse clip and switch blade assemblies substantially identical to those shown in US. Patent No. 2,654,011 and each including a fuse clip 32, a blade mounting member 34, and a flat generally V-shaped or Y-shaped switch blade 36 pivotably mounted adjacent a free end of one of its leg portions on a rivet 38 supported in a pair of opposed leg portions of the blade mounting member 34.

As illustrated, the duct plug 20 is intended for use in a three-phase, four-wire system. Thus, FIG. 2 shows four pairs of plug-in jaws 40 clamped respectively on four bus bars 42 of the bus duct 26. The pairs of plug-in jaws 40 are secured respectively to four conductive strap members 43, 44, 45, and 46 which extend through a flanged opening (not shown) in the rear wall portion 22b of the box 22 and through the base 28. The inner end portions of the strap members 43, 44, and 45 are connected respectively to three pairs of stationary contact jaws 48 mounted on the base 28 and only partially shown in FIG. 3 but identical to stationary contact jaws! of the switch of the aforesaid patent. The free end portions of the other leg portions of the switch blades 36 are receivable respectively in the pairs of stationary contact jaws 48, as will be understood. An arc suppressor assembly 50, shown in FIG. 4 but omitted for clarity in FIG. 3, is secured to the base 28 over the jaws 48, the arc suppressor assembly 50 being identical to that of the aforesaid patent.

The inner end portion of the strap member 46 is connected by a screw 51 to a neutral wire connector 52 mounted on an insulating base 54. The base 54 and an additional insulating shield 55 are secured to the rear wall portion 22b of the box 22 by a screw 56. It will be understood that for a three-phase, three-wire system, the screw 56, shield 55, base 54, connector 52, and the strap member 46 and its associated pair of plug-in jaws 40 and the corresponding bus bar 42 may be omitted.

An insulating base 58 and an additional insulating shield 59 are secured to the rear wall portion 22b of the box 22 by a pair of screws 60. Secured to the base 58 are three fuse clip and load terminal assemblies each including a load terminal 62 and a fuse clip 32 reversed from the corresponding fuse clip 32 associated with a switch blade 36. The three pairs of fuse clips 32 are adapted respectively to receive three fuses 64 shown in phanton in FIG. 3..

The blades 36 are driven between 0N and OFF positions by a pivotable bail member 66 but are insulated therefrom by an insulator 68 trapped therebetween. A lower end portion 661: of the bail member 66 is pivoted in an extruded portion of a bottom wall portion 226 (FIG. 3) of the box 22, while an upper end portion 66b of the bail member 66 is flattened, mounted on a pin 70 supported at one end in a top wall portion 22d of the box 22 and supported at the other end in a bottom wall portion of a generally channel-shaped bracket 72. The free end portions of the side wall portions of the bracket 72 are bent away from each other to provide a pair of flanges secured to the wall portion 22d by a pair of rivets 73 and 74.

Also mounted on the pin 70 are an operating member 76 for the bail member 66 and a drive cam 78 for the operating member 76. The operating member 76 includes a pair of spaced bent-over tongue portions 76a and 76b which straddle the portion 66b of the bail member 66 and drive the bail member selectively to ON and OFF positions corresponding to ON and OFF positions of the switch blades 36. The bracket 72 is provided with a pair of lanced portions 72a and 72b which respectively limit the pivotal movement of the bail member 66 in opposite directions. A stop pin 80 mounted adjacent opposite ends 3 respectively in the bracket 72 and top wall portion 22d limits pivotal movement of the operating member 76 in opposite directions.

The drive cam 78 is provided with a bent-over driving tongue portion 78a which fits within a peripheral recess in the operating member 76 and drives the operating member 76 selectively in opposite directions. In the latter portion of its pivotal movement in either direction, the operating member 76 is driven with a snap action by an overcenter spring mechanism which is charged during the first portion of the pivotal movement of the operating member 76, the overcenter spring mechanism including a drive arm 82 reciprocally mounted adjacent one end in a leg portion of the bracket 72, a drive pin 84 mounted in a generally T-shaped slot 76c in the operating member 76 and pivotally connecting the other end portion of the drive arm 82 to the operating member 76, and a compression spring 86 mounted on the drive arm 82.

The drive cam 78 includes an interlock arm 78b having a bent-over end portion 780 which normally cooperates with a latch (not shown) on the inner side of the cover 24 when the switch blades 36 are in ON position to prevent opening of the cover 24. However, a knowledgeable person may defeat this interlock by turning a screw 88 (FIG. 1) to release the latch (not shown) from the bent-over end portion 780 and permit opening of the cover 24 when the switch blades 36 are in ON position. The cover 24 is normally latched closed, regardless of the position of the switch blades 36, by a latch 89 which is pivotally mounted on a left side wall portion 22e of the box 22, and which is provided with a hole 89a for reception of a padlock hasp.

The drive cam 78 also includes a driven arm 78d an outer end portion of which carries a driving pin 90. The driving pin 90 is riveted or otherwise secured adjacent one end to the driven arm 78d. The other end portion of the driving pin 90 is received in a slotted short leg portion 92a of a generally L-shaped driving lever 92 (FIG. 7) a long leg portion 92b of which is pivotally mounted on a pin 94 secured in the left side wall portion 22e of the box 22. The lever 92 is driven by a driving pin 96 which extends through a slot 920 in the lever 92 and also through an arcuate slot 221 in the side wall portion 22e of the box 22. The pin 96 is mounted on a handle 98 (FIGS. 1-5) which is pivotally mounted on the outside of the side wall portion 22e by means of a pin 100 extending through the handle and the side wall portion 22e.

An interlock member 102 is pivotally connected to the handle 98 by means of a pin 104 and slidably connected to the side wall portion 22e by means of a pin 106 disposed in a slot 102a (FIG. 2) of the interlock member and secured in the side wall portion 22e. As explained hereinafter, the interlock member 102 prevents the plug-in jaws 40 of the duct plug from being connected to or disconnected fro-m the bus bars 42 of the bus duct 26 while the switch blades 36 are in ON position.

The duct plug 20 is provided with a pair of hook members 108 and 109 secured respectively to the left side wall portion 22e and the rear wall portion 22b of the box 22 in any suitable manner. In the plugging of the duct plug 20 into the bus duct 26 with the switch blades 36 in OFF position, the duct plug is first hung by the hook members 108 and 109 over an upper edge portion of the housing of the bus duct 26, and a screw 110 (FIGS. 1, 2, 3, 4, 5, 8, and 10) is then tightened to pull the plug-in jaws 40 onto the bus bars 42 by means hereinafter described.

A generally L-shaped bracket 112 is secured in spaced relationship to the side wall portion 222 by means of a pin 114. Between the bracket 112 and the side wall portion 22e an elongated actuating member 116 is slidably mounted on a pair of pins including the pin 114 and a pin 118, a pair of elongated slots 116a and 1 1612 (FIGS.

2 and 8) being provided in the actuating member 116 and the pins 114 and 118 being disposed respectively therein.

Adjacent its front end, the actuating member 116 is provided with a flange portion 1160 through which the screw extends. In addition to a head portion 110a, the screw 110 includes an integral collar portion 110b. The flange portion 116:: is disposed between the head portion 110a and the collar portion 11% and is provided with a keyhole-shaped slot 116d, shown only in section in FIG. 8, it being understood that in assembling, the collar portion 110]; is first inserted through the larger portion of the slot 116d and the screw 110 is then shifted to the smaller portion of the slot 116d. The screw 110 is threaded into the bracket 112, so that when the screw is turned, the actuating member 116 is shifted on the pins 114 and 118.

A generally rectangular bracket 120 having three flange portions 120a, 120b, and 1200 is secured at the flange portion 120a in any suitable manner to the outer surface of the rear wall portion 22]). A clamping member 122, best shown in FIG. 4, is pivotally but loosey mounted on the bracket 120 by means of a pin or rivet 124. The clamping member 122 includes three arms 122a, 122b, and 1220, the arms 122a and 122c extending generally in opposite directions from each other and the arm 122k being disposed generally at right angles to the arms 122a and 1220. The actuating member 116 is provided with an aperture 116e (FIGS. 2 and 8) in which the outer end portion of the arm 122a is received, and is also provided with a normally horizontal flange portion 116 for purposes later described.

The flange portion 1200 of the bracket 120 is provided with an inclined slot 120d (FIG. 10) through which the arm 1221) projects. The arm 1221) is provided with an upturned outer end portion 122d. The flange portion 12% is provided with an aperture 120e, partially shown in FIG. 2, through which the arm 1220 projects. The arm 122c is provided with an upturned clamping end portion 122e.

A bracket 126 is secured to the wall portion 222 of the box 22 between the wall portion 22e and the handle 98, as best shown in FIG. 9. The bracket 126 is provided with a pair of holes 126a and the handle 98 is provided with a corresponding pair of holes 98a, as best shown in FIGS. 2 and 3, in order that the handle 98 may be padlocked in the OFF position.

When the screw 110 is turned clockwise into the bracket 112, the flange portion 1160 is carried along between the integral collar portion 110k and the head portion 110a and the actuating member 116 is shifted toward the left in FIG. 2 along with the outer end portion of the arm 122a. The clamping member 122 is thus turned clockwise in FIG. 5 and the arm 122b is moved toward the right in FIG. 5 and toward the left in FIG. 10. Due to the inclination of the slot 120d, movement of the arm 122b toward the left in FIG. 10 causes the clamping member 122 to rise in a manner which might be described as pivoting clockwise in FIG. 10 about the outer end portion of the arm 122a. The portion 122d of the arm 122b and the clamping portion 122e of the arm 122c thus rise as the clamping member 122 pivots clockwise in FIG. 5. When the duct plug 20 is being installed on a bus duct 26, the rising of the clamping portion 122e as the clamping member 122 pivots clockwise in FIG. 5 causes the clamping portion 122e to bear against a lower inner edge portion of the housing of the bus duct 26, as shown in FIG. 2, to pull the plug-in jaws 40 onto their respective bus bars 42.

When the screw 110 is turned counterclockwise out of the bracket 112, as to the broken-line position thereof shown in FIG. 2, the actuating member 116 and clamping member 122 move oppositely to the manner described above for clockwise turning of the screw 110,

as to the broken-line positions thereof shown respectively in FIGS. 2 and 4.

In FIG. 2 the full-line position of the actuating member 116 illustrates its position corresponding to clamped position of the clamping portion 122e against a lower inner edge portion of the housing of the bus duct 26, and the broken-line position illustrates its position corresponding to unclamped position of the clamping portion 122e, or the position of the clamping portion 122a for installation of the duct plug 20 on the bus duct 26. Also in FIG. 2, the full-line positions of the handle 98 and the interlock member 102 illustrate their positions corresponding to the ON position of the switch blades 36, and the broken-line positions illustrate their positions corresponding to OFF position of the switch blades 36. When the actuating member 116 is in the full-line position, the interlock member 102 clears the flange portion 116f and may be shifted to its full-line position corresponding to the ON position of the switch blades 36. However, if an attempt is made to install the duct plug 20 on the bus duct 26 when the switch blades 36 are in ON position, the upturned outer end portion 122d of the arm 122b will interfere with the housing of the bus duct 26 and prevent the plugging of the jaws 40 onto the bus bars 42. In order to prevent interference between the end portion 122d and the housing of the bus duct 26, the actuating member 116 must be shifted rightwardly in FIG. 2 to its broken-line position to lower the end portion 122d, the clamping member 122 falling by gravity as the arm 122b moves downwardly in the inclined slot 120d (FIG. and the actuating member 116 cannot be shifted to its broken-line position unless the interlock member 102 is shifted upwardly in FIG. 2 to its brokenline position by the turning of the handle 98 to its OFF position. Thus, the duct plug 20 cannot be plugged into the bus duct 26 while the switch blades 36 are in ON position. Further, when the actuating member 116 is in its broken-line position in FIG. 2, the flange portion 116; interferes with attempted shifting of the interlock member 102 to its lower full-line by the turning of the handle 98 to its ON position. Therefore, the duct plug 20 must be fully clamped on the bus duct 26 by the shifting of the actuating member 116 to its full-line position before the switch blades 36 can be shifted to ON position.

If an attempt is made to remove the duct plug 20 from the bus duct 26 while the switch blades 36 are in ON position, the clamping portion 122e of the clamping member 122 will interfere with the lower inner edge portion of the housing of the bus duct 26 which it normally clamps. In order to lower the clamping portion 122e out of interfering relationship with thehousing of the bus duct, the actuating member 116 must be shifted to its broken-line position in FIG. 2, and before this can be done, the interlock member 102 must be shifted upwardly in FIG. 2 to its broken-line position by the turning of the handle 98 to its OFF position. Therefore, the duct plug 20 cannot be removed from the bus duct 26 while the switch blades 36 are in ON position.

We claim:

1. For plugging into an elongated horizontally extending plug-in bus duct having a plurality of elongated horizontally extending vertically spaced parallel bus bars, a bus duct plug comprising a box having a rear wall portion and a side wall portion generally perpendicular to each other, each of said rear and side wall portions also being generally perpendicular to a horizontal plane when said bus duct plug in a normal position of use is plugged into an elongated horizontally extending plug-in bus duct having a plurality of elongated horizontally extending vertically spaced parallel bus bars, a plurality of stationary contact members in said box, a plurality of plugin terminal means having portions spaced outwardly of said box from said rear wall portion and electrically connected respectively to a plurality of elongated horizontally extending vertically spaced parallel bus bars when said and disconnected respectively from bus duct plug is in the normal position of use, a plurality of conductor means electrically connecting said plug-in terminal means respectively with said stationary contact members, an operating handle mounted outside said box on said side wall portion, said operating handle being movable alternatively to ON and OFF positions, a plurality of generally flat switch blades disposed in said box in flatwise-parallel relationship to each other and pivotable edge between ON and OFF positions corresponding respectively to the ON and OFF positions of said operating handle, said switch blades when in the ON position thereof being engaged respectively with said stationary contact members and when in the OFF position thereof being disengaged respectively from said stationary contactrnembers, and means operatively connecting said operating handle and switch blades, said switch blades also being disposed in flatwise-parallel relationship to a horizontal plane when said bus duct plug is in the normal position of use.

2. For plugging into an elongated horizontally extending plug-in bus duct having a plurality of elongated horizontally extending vertically spaced parallel bus bars, a bus duct plug comprising a box having a rear wall portion generally perpendicular to a horizontal plane when said bus duct plug in a normal position of use is plugged into an elongated horizontally extending plug-in bus duct having a plurality of elongated horizontally extending vertically saced parallel bus bars, a plurality of stationary contact members in said box, a plurality of plug-in terminal means having portions spaced outwardly of said box from said rear wall portion and electrically connected respectively to a plurality of elongated horizontally extending vertically spaced parallel bus bars when said bus duct plug is in the normal position of use, a plurality of conductor means electrically connecting said plug-in terminal means respectively with said stationary contact members, a plurality of switch blades in said box, said switch blades being movable between ON and OFF positions and when in the ON position thereof being engaged respectively with said stationary contact members and when in the OFF position thereof being disengaged respectively from said stationary contact members, an operating handle operable from the outside of said box and movable alternatively to ON and OFF positions corresponding to the ON and OFF positions of said switch blades, means operatively connecting said operating handle and switch blades, and interlock means mounted on and visible from the outside of said box, said interlock means when said handle and switch blades are in ON position alternatively preventing said plug-in terminal means from being electrically connected respectively to a plurality of elongated horizontally extending vertically spaced parallel bus bars of an elongated horizontally extending plug-in bus duct.

3. A bus duct plug as claimed in claim 2, wherein said switch blades are generally fiat, are disposed in flatwise-parallel relationship to each other, are pivotable edgewise between said ON and OFF positions, and are disposed in flatwise-parallel relationship to a horizontal plane when said bus duct plug is in the normal position of use.

4. A bus duct plug as claimed in claim 2, wherein said box includes a side wall portion generally perpendicular to said rear wall portion and also generally perpendicular to a horizontal plane when said bus duct plug is in the normal position of use, and said operating handle is mounted outside said box on said side wall portion.

5. A bus duct plug as claimed in claim 2, wherein said switch blades are generally flat, are disposed in flatwiseparallel relationship to each other, and are pivotable edgewise between said ON and OFF positions, wherein said box includes a side wall portion generally perpendicular to said rear wall portion, wherein said operating handle is mounted outside said box on said side wall portion,

and wherein said switch blades are disposed in flatwise; parallel relationship to a horizontal plane and said side wall portion is generally perpendicular to a horizontal plane when said bus duct plug is in the normal position of use.

6. A bus duct plug as claimed in claim 2, wherein said box includes a side wall portion generally perpendicular to said rear wall portion and also generally perpendicular to a horizontal plane when said bus duet plug is in the normal position of use, wherein said operating handle is mounted outside said box on said side wall portion, and wherein said interlock means includes a clamping member spaced outwardly of said rear wall portion of said box, mounting means mounting said clamping member for pivotal movement about an axis generally vertical in the normal position of use of efiective as said clamping member is pivoted about said vertical axis for pivoting one end portion of said clamping member about an axis generally horizontal in the normal position of use of the bus duct plug and disposed adjacent the other end portion of said clamping member, an actuating member slidably mounted on said side wall portion and connected adjacent one end to said other end portion of said clamping member, a bracket on said side wall portion, a driving screw threadedly mounted in said bracket and connected to the other end portion of said actuating member so as to move said actuating member and clamping member when turned, and an interlock member slidably mounted on said side wall portion and connected adjacent one end to said operating handle, said other end portion of said actuating member interfering with the other end portion of said interlock member and preventing movement of said operating handle to ON position unless said screw is turned sufliciently into said bracket to move said actuating member out of interfering relationship with said interlock member while moving said clamping member toward a clamping position with respect to a housing of a bus duct.

the bus duct plug, means 7. A bus duct plug as claimed in claim 6, wherein said clamping member is generally flat, extends generally hori zontally in the normal position for use of the bus duct plug, and includes three arms a first of which is connected to said actuating member and a second of which extends oppositely to the first and is provided with an upturned clamping end portion, said mounting means for said clamping member includes a generally fiat bracket secured to the outside of said rear wall portion of said box and extending generally horizontally in the normal position of use of the bus duct plug, and said means for pivoting said clamping member about said generally horizontal axis includes a flange on the mounting bracket for said clamping member extending generally parallel to said rear wall portion of said box in spaced relationship thereto and having an inclined slot therein, and a third arm on said clamping member extending through said inclined slot in a direction generally perpendicular to the other two arms of said clamping member.

8. A bus duct plug as claimed in claim 7, wherein said third arm of said clamping member is provided with an upturned end portion which interferes with a housing of a bus duct if an attempt is made to install the bus duct plug on a bus duct when said actuating member is in a position permitting free movement of said interlock mem ber and movement of said operating handle to ON position.

References Cited UNITED STATES PATENTS ROBERT K. SCHAEFER, Primary Examiner. J. R. SCOTT, Assistant Examiner;

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,339 ,038 August 29 1967 George N. Jorgensen et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 4 line 22 for "loosey" read loos e1 colum 6, l1ne 9, for "edge" read edgewise line 28, for "saced read spaced column 8, line 3, for "for" read of Signed and sealed this 24th day of September 1968.

SEAL) \ttest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, J r.

Xttesting Officer 

1. FOR PLUGGING INTO AN ELONGATED HORIZONTALLY EXTENDING PLUG-IN BUS DUCT HAVING A PLURALITY OF ELONGATED HORIZONTALLY EXTENDING VERTICALLY SPACED PARALLEL BUS BARS, A BUS DUCT PLUG COMPRISING A BOX HAVING A REAR WALL PORTION AND A SIDE WALL PORTION GENERALLY PERPENDICULAR TO EACH OTHER, EACH OF SAID REAR AND SIDE WALL PORTIONS ALSO BEING GENEALLY PERPENDICULAR TO A HORIZONTAL PLANE WHEN SAID BUS DUCT PLUG IN A NORMAL POSITION OF USE IF PLUGGED INTO AN ELONGATED HORIZONTALLY EXTENDING PLUG-IN BUS DUCT HAVING A PLURALIITY OF ELONGATED HORIZONTALLY EXTENDING VERTICALLY SPACED PARALLEL BUS BARS, A PLURALITY OF STATIONARY CONTACT MEMBERS IN SAID BOX, A PLURALITY OF PLUGIN TERMINAL MEANS HAVING PORTIONS SPACED OUTWARDLY OF SAID BOX FROM SAID REAR WALL PORTION AND ELECTRICALLY CONNECTED RESPECTIVELY TO A PLURALITY OF ELONGATED HORIZONTALLY EXTENDING VERTICALLY SPACED PARALLEL BUS BARS WHEN SAID BUS DUCT PLUG IS IN THE NORMAL POSITION OF USE, A PLURALITY OF CONDUCTOR MEANS ELECTRICALLY CONNECTING SAID PLUG-IN TERMINAL MEANS RESPECTIVELY WITH SAID STATIONARY CONTACT MEMBERS, AN OPERATING HANDLE MOUNTED OUTSIDE SAID BOX ON SAID SIDE WALL PORTION, SAID OPERATING HANDLE BEING MOVABLE ALTERNATIVELY TO ON AND OFF POSITIONS, A PLURALITY OF GENERALLY FLAT SWITCH BLADES DISPOSED IN SAID BOX IN FLATWISE-PARALLEL RELATIONSHIP TO EACH OTHER AND PIVOTABLE EDGE BETWEEN ON AND OFF POSITIONS CORRESPONDING RESPECTIVELY TO THE ON AND OFF POSITIONS OF SAID OPERATING HANDLE, SAID SWITCH BLADES WHEN IN THE ON POSITION THEREOF BEING ENGAGED RESPECTIVELY WITH SAID STATIONARY CONTACT MEMBERS AND WHEN IN THE OFF POSITION THEREOF BEING DISENGAGED RESPECTIVELY FROM SAID STATIONARY CONTACT MEMBERS, AND MEANS OPERATIVELY CONNECTING SAID OPERATING HANDLE AND SWITCH BLADES, SAID SWITCH BLADES ALSO BEING DISPOSED IN FLATWISE-PARALLEL RELATIONSHIP TO A HORIZONTAL PLANE WHEN SAID BUS DUCT PLUG IS IN THE NORMAL POSITION OF USE. 